The present invention relates to an artificial jointless foot having an incompressible wooden core forming an upper connecting surface, and with elastic synthetic materials connected to the core for forming the foot shape and ensuring a flexible rolling action. The wooden core forms, on the connecting surface, a dorsal stop for an adaptor connectable to the core and tiltable relative to the core.
Jointless feet have been known for a long time and are in frequent use. By means of a skillful arrangement of flexible materials on the wooden core, jointless feet can be designed so that they are in no way inferior to and can even surpass a jointed foot in terms of walking ease.
The wooden core of jointless feet of this type should be produced from wood which is as light as possible. Light and inexpensive wood can perform all the functions of the core of such a jointless foot. The disadvantage associated with such a soft wood is that pronounced wear occurs on its connecting surface in the region of the dorsal stop. This pronounced wear arises because a metal adaptor connected to the foot exerts a load on the surface during each rolling action. During rolling, the adaptor resting on the connecting surface of the wooden core presses with its front edge on this connecting surface. When light wood is used, the connecting surface can quickly become deformed at the location of the dorsal stop. As a result of the play developed, the strength of the connection to the adaptor is no longer guaranteed and undesirable movements of the foot can occur. Furthermore, the screw connection of the adaptor can break resulting in the entire foot prosthesis becoming useless and capable of causing an accident.
This high probability of damage resulted in the use of expensive hard wood to solve the problem, but the use of hard wood increased the weight of the foot prosthesis substantially.
Attempts have already been made to avoid the use of expensive heavy wood by reinforcing the connecting surface of the light wooden core in the region of the dorsal stop. However, an attached metal plate reinforcement can cause an undesirable sliding movement of the adaptor on the connecting surface. Attempts have also been made to replace the surface of the wooden core by a hard-wood insert at the location of the dorsal stop. It was shown, however, that, because of the high load, it is not possible to make a stable connection between the hard-wood insert and the wooden core by means of adhesive bonding or the like.